TREE DEATH FROM BARK BEETLES: CARBON STARVATION OR HYDRAULIC FAILURE

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: MCINTIRE-STENNIS
• Reporting Frequency: Annual
• Accession No.: 0230732
• Project Start Date: Jul 1, 2012
• Project End Date: Jun 30, 2016
• Program Code: [(N/A)]- (N/A)

Recipient Organization
NORTHERN ARIZONA UNIVERSITY
(N/A)
FLAGSTAFF,AZ 86011

Performing Department
School Of Forestry

Non Technical Summary
The ability of several bark beetle species to attack and kill trees is overwhelmingly evident in North America where several species have or are developing outbreaks of exceptional size; however, despite many decades of research, the processes involved in tree death after beetle attack are still poorly understood. To effectively resolve this issue, scientists need to understand the respective role of bark beetles and their symbiotic fungi in the processes that lead to tree mortality. The close association of tree-killing bark beetles and fungi, and the fact that trees are nutritionally poor, have led many researchers to suspect that bark beetles are either dependent on fungi to kill trees and/or, for nutrition and reproductive success. A comprehensive, systematic study that clearly documents the temporal change in tree physiological function post-beetle attack and concurrent with beetle and fungal establishment is desperately needed. Further, a better understanding of the nature of the symbiotic relationship between beetles and their associated fungi will advance understanding of other insect/fungal relationships. Our study uses a full factorial design and a cross-disciplinary approach to examine the symbiotic relationship between beetles and fungi and the role of each agent in mortality of ponderosa pine in northern Arizona. The overarching goal of this project is to determine the nature of the beetle/fungus relationship, i.e. do bark beetles need fungi to be successful To achieve this goal, our study will examine tree physiological processes that are disrupted during and after bark beetle attack to determine the role of each of the respective agents (beetles, fungi) in tree killing, and will document tree processes that must be disrupted for successful bark beetle attack.

Animal Health Component

(N/A)

Research Effort Categories

Basic

(N/A)

Applied

(N/A)

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
211	0612	1130	50%
212	0612	1160	50%

Knowledge Area
212 - Pathogens and Nematodes Affecting Plants; 211 - Insects, Mites, and Other Arthropods Affecting Plants;

Subject Of Investigation
0612 - Conifer forests of the West;

Field Of Science
1130 - Entomology and acarology; 1160 - Pathology;

Keywords

tree killing

bark beetle

fungi

insect

Goals / Objectives
The overall project goal is to investigate physiological mechanisms of tree death in ponderosa pine trees during and after bark beetle attacks. Specifically, the project will quantify changes in tree physiological function from two different biotic agents (bark beetles and fungi) that enter the subcortical environment of trees during bark beetle attacks to determine whether tree death occurs from: a) mechanical girdling of the tree via beetle feeding and reproduction resulting in carbon starvation of resin defenses; b) a loss of tree hydraulic conductance due to the penetration of fungi into the sapwood, leading to hydraulic failure; c) a combination of carbon starvation and hydraulic failure. The following hypotheses will be tested: H1: Fungi + beetle is a mutualism with fungi gaining transport to a new host and bark beetles depending on fungi to: 1) overcome host defenses and/or, 2) aid in killing of host trees and/or, 3) provide nutrition. General support for this hypothesis will be that beetle success (herein defined as more trees killed and/or higher beetle reproductive fitness) is higher when fungi are present than when fungi are absent. H2: Presence of fungi has no impact on bark beetle success (commensalism). Support for this hypothesis will be no difference in bark beetle success with or without fungi. H3: Fungi have a negative impact on bark beetle success (antagonism). Support for this hypothesis will be lower bark beetle success in the presence of fungi than in their absence. Project results will increase understanding of forest community ecology by clarifying the nature of the bark beetle/fungus symbiosis. Understanding the nature of this symbiosis will enhance our understanding of characteristics important for tree resistance to bark beetles by clarifying whether resistance to bark beetles is of greater importance than resistance to fungi. Results from this research will advance knowledge of tree defenses against bark beetles by clarifying mechanisms that cause tree death in conifer forests. The project also may identify new treatments to save high value pines from death during bark beetle attacks, such as fungicide injections into the sapwood, rather than prophylactic insecticide sprays. Specific outputs include: 1) Training of a Ph.D. student whose dissertation will be focused on the project; 2) several peer-reviewed manuscripts about the project.

Project Methods
The study will use a cross-disciplinary approach to examine the symbiotic relationship between beetles and fungi and the role of each agent in tree mortality via a novel experimental design that will manipulate both bark beetles and fungi on mature ponderosa pines located in northern Arizona. We will use a full factorial 2x2 experimental design with factors of bark beetle attacks (with (B+) and without (B-)) and fungi presence (with (F+) and without (F-)). We will assess response to the experimental treatments with measurements of tree resin defense, water and carbon relations, tree survival, fungal growth, and bark beetle performance on replicated trees in each treatment over at least two years after treatment.

Progress 07/01/12 to 06/30/16

Outputs
Target Audience:Foresters and entomologists in the western United States. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Onestudent was trainedand graduated with a Ph.D. inforest entomology. The student pipelined directly to the professional workforce as a Forest Health Specialist, USDA Forest Service. Research experience was provided to three undergraduate students in forestry. How have the results been disseminated to communities of interest?Results have been dissimilated via conference presentations, published conference abstracts, book chapters, and a journal article. At least one more journal article is forthcoming. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? New scientific knowledge produced by the project includes: 1) Bark beetle-caused mortality of ponderosa pine requires tree stress. Most trees are well-defended against beetles in the absence of stress, and are resistant to stress in the absence of bark beetles. 2) Support for hydraulic failure and compromised tree defense as mechanisms by which bark beetles kill ponderosa pine during periods of drought stress. 3) Fungi carried by bark beetles requires active inoculation of trees by beetle feeding in order to colonize and kill trees during drought. Inoculation of trees with fungi in the absence of beetle feeding does not harm trees.

Publications

• Type: Journal Articles Status: Published Year Published: 2017 Citation: Adams, H.D., M.J.B. Zeppel, W.R.L. Anderegg, H. Hartmann, S.M. Landh�usser, D.T. Tissue, T.E. Huxman, P.J. Hudson, T.E. Franz, C.D. Allen, L.D.L. Anderegg, G.A. Barron-Gafford, D.J. Beerling, D.D. Breshears, T.J. Brodribb, H. Bugmann, R.C. Cobb, A.D. Collins, LT. Dickman, H. Duan, B.E. Ewers, L. Galiano, D. A. Galvez, N. Garcia-Forner, ML. Gaylord, M.J. Germino, A. Gessler, U.G. Hacke, R. Hakamada, A. Hector, M.W. Jenkins, J.M. Kane, T.E. Kolb, D.J. Law, J. D. Lewis, J. M-Limousin, A.K. Macalady, J. Mart�nez-Vilalta, M. Mencuccini, P.J. Mitchell, J.D. Muss, M.J. O'Brien, A.P. O'Grady, R. E. Pangle, E.A Pinkard, F.I. Piper, J.A. Plaut, W.T. Pockman, J. Quirk, K. Reinhardt, F. Ripullone, A. Sala, S. Sevanto, J.S. Sperry, R. Vargas, M. Vennetier, D.A. Way, C. Xu, E.A. Yepez, N.G. McDowell. 2017. A multi-species synthesis of physiological mechanisms in drought-induced tree mortality. Nature Ecology and Evolution DOI: 10.1038/s41559-017-0248-x.
• Type: Conference Papers and Presentations Status: Published Year Published: 2017 Citation: Hicke, J.A., T.E. Kolb, C.J. Fettig, M.P. Ayres, B.J. Bentz, R. Mathiasen, J.E. Stewart, and A.S. Weed. Impacts of drought on forest insects and diseases in the United States (abstract). Annual Meeting of the Ecological Society of America, 7-11 August 2017, Portland, OR.
• Type: Conference Papers and Presentations Status: Published Year Published: 2017 Citation: Gaylord, M.L., S.J. Burr, R.W. Hofstetter, T.E. Kolb, N. McDowell. 2017. The impacts of drought on tree defenses and bark beetle attacks in southwestern pines (abstract). 2017 Meeting of the Western Forest Insect Working Conference, Jackson, WY.
• Type: Conference Papers and Presentations Status: Awaiting Publication Year Published: 2017 Citation: Kolb, T.E., H.D. Adams, M.L. Gaylord. 2017. Tree mortality during drought: the biotic connection. International Union of Forestry Research Organizations, 125th Anniversary Congress, Freiburg, Germany, Sept. 20, 2017.

Progress 10/01/14 to 09/30/15

Outputs
Target Audience:Foresters and entomologists in the western United States. Changes/Problems:We request a one-year no-cost extension of the project to go through 6/30/17. What opportunities for training and professional development has the project provided?Training in forestry, entomology and pathology was provided to one doctoral-level graduate student in the School of Forestry, Northern Arizona University. Also, training in basic research methods was provided to one undergraduate student in forestry. How have the results been disseminated to communities of interest?PI Kolb published two book chapters that are related to the project. A doctoral dissertation and journal articles are forthcoming. What do you plan to do during the next reporting period to accomplish the goals?The doctoral student should finish his dissertation during this period. The student and PI will submitt at least two manuscripts to referred journals.

Impacts
What was accomplished under these goals? The project team finished the field measurements and samping. Analysis of these data is in progress.

Publications

• Type: Book Chapters Status: Published Year Published: 2015 Citation: Kolb, T.E., C.J. Fettig, B.J. Bentz, J.E. Stewart, A.S. Weed, J.A. Hicke, M.P. Ayres. 2016. Chapter 6: Forest insect and fungal pathogen responses to drought. Pages 113-133 In: Vose, J., J. Clark, C. Luce, T. Patel-Weynand (editors), Effects of Drought on Forests and Rangelands in the United States. USDS Forest Service General Technical Report WO-93b. http://www.fs.fed.us/sites/default/files/DROUGHT_book-web-1-11-16.pdf Raffa, K.F., B.H. Aukema, B.J. Bentz, A.L. Carroll, J.A. Hicke, T.E. Kolb. 2015. Responses of tree-killing bark beetles to a changing climate. Pages 173-201 In: Bjorkman, C., P. Niemela (editors), Climate Change and Insect Pests. CABI International Press.

Progress 10/01/13 to 09/30/14

Outputs
Target Audience: Foresters and entomologists in the western United States Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Training in forestry, entomology and pathology was provided to one doctoral-level graduate student in the School of Forestry, Northern Arizona University. Also, training in basic research methods was provided to one undergraduate student in forestry. How have the results been disseminated to communities of interest? No dissemination activities occurred in this year. What do you plan to do during the next reporting period to accomplish the goals? All studies described above will be continued next year, which should be the last year of data collection. Training of the graduate student will continue.

Impacts
What was accomplished under these goals? The project team successfully implemented water stress, bark beetle attack, and fungal invasiontreatments to mature ponderosa pine trees in a replicated field design. We measured tree resin defenses, water stress, and canopy stomatal conductance and photosynthesis between May and November 2014. We also collected sapwood samples for analysis of fungal invasion. Analysis of these data is in progress.

Publications

• Type: Book Chapters Status: Awaiting Publication Year Published: 2015 Citation: Raffa, K.F., B.H. Aukema, B.J. Bentz, A.L. Carroll, J.A. Hicke, T.E. Kolb. In press. Responses of tree-killing bark beetles to a changing climate. In: Bjorkman, C., P. Niemela (editors), Climate Change and Insect Pests. CABI Press.

Progress 10/01/12 to 09/30/13

Outputs
Target Audience: Target audiences include approximately 300 forest managers, entomologists, and pathologists that attended four talks on the project at the: 1) 12th Biennial Conference of Science and Management on the Colorado Plateau, September 16-19, 2013, Flagstaff, Arizona 2) 64th Western Forest Insect Work Conference, March 4-7, 2013, Coeur d'Alene, Idaho. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Training in forestry, entomology and pathology was and is being provided to one doctoral-level graduate student in the School of Forestry, Northern Arizona University. Also, training in basic research methods was and is being provided to one undergraduate in forestry, and one undergraduate minority student as part of a summer reserarch internship. How have the results been disseminated to communities of interest? Four presentations about the project were given to foresters, entomologists, and pathologist: Kolb, T.E., M.L. Gaylord. 2013. Interactions among drought, tree stress, and bark beetles in forests and woodlands of the southwestern U.S. (abstract). Proceedings of the 2013 Western Forest Insect Work Conference, March 4-7, 2013, Coeur d' Alene, Idaho. Kolb, T.E., M.L. Gaylord. 2013. Interactions among drought, tree stress, and bark beetles on the Colorado Plateau (abstract). Proceedings of the 12th Biennial Conference of Science and Management on the Colorado Plateau, September 16-19, 2013, Flagstaff, Arizona. Burr, S.J., T.E, Kolb, R.W. Hofstetter, M.K. Gaylord. 2013. Physiological impacts to Pinus ponderosa following colonization of bark beetles and their associated fungi (abstract). Proceedings of the 64th Western Forest Insect Work Conference, March 4- 7th, 2013, Coeur d'Alene, Idaho. Reyes, T., S. Burr, R. Hofstetter, T. Kolb. 2013. Attractiveness of frontaline and endo-brevicomin aggregation pheromones to Dendroctonus bark beetles (abstract). Proceedings of the 12th Biennial Conference of Science and Management on the Colorado Plateau, September 16-19, 2013, Flagstaff, Arizona. What do you plan to do during the next reporting period to accomplish the goals? All studies described above will be continued. Training of graduate student will continue.

Impacts
What was accomplished under these goals? A doctoral-level graduate student, Stephen Burr, was recruited for the project in 2012. He worked with the project PI to start a novel experimental study in 2013 on the role of fungi, bark beetles, and tree stress in tree physiological disfunction, and a second project on performance of different bark-beetle-vectored fungi in ponderosa pine trees. These projects are entering their second year and will be continued for at least one more year. An additional pilot project was started on using genomics to identify the microbial community carried by bark beetles. The project team described the main project to natural resource managers and scientists in four different presenations in 2013.

Publications

• Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Burr, S.J., T.E, Kolb, R.W. Hofstetter, M.K. Gaylord. 2013. Physiological impacts to Pinus ponderosa following colonization of bark beetles and their associated fungi (abstract). Proceedings of the 64th Western Forest Insect Work Conference, March 4-7th, 2013, Coeur dAlene, Idaho. Kolb, T.E., M.L. Gaylord. 2013. Interactions among drought, tree stress, and bark beetles in forests and woodlands of the southwestern U.S. (abstract). Proceedings of the 2013 Western Forest Insect Work Conference, March 4-7, 2013, Coeur d Alene, Idaho. Kolb, T.E., M.L. Gaylord. 2013. Interactions among drought, tree stress, and bark beetles on the Colorado Plateau (abstract). Proceedings of the 12th Biennial Conference of Science and Management on the Colorado Plateau, September 16-19, 2013, Flagstaff, Arizona. Reyes, T., S. Burr, R. Hofstetter, T. Kolb. 2013. Attractiveness of frontaline and endo-brevicomin aggregation pheromones to Dendroctonus bark beetles (abstract). Proceedings of the 12th Biennial Conference of Science and Management on the Colorado Plateau, September 16-19, 2013, Flagstaff, Arizona.

Progress 07/01/12 to 09/30/12

Outputs
Target Audience: Target audiences include approximately 300 forest managers, entomologists, and pathologists that attendedfour talks on the project at the: 1) 12th Biennial Conference of Science and Management on the Colorado Plateau, September 16-19, 2013, Flagstaff, Arizona 2) 64th Western Forest Insect Work Conference, March 4-7, 2013, Coeur d'Alene, Idaho. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Training in forestry, entomology and pathology was and is being provided to one doctoral-level graduate student in the School of Forestry, Northern Arizona University. Also, training in basic research methods was and is being provided to one undergraduate in forestry, and one undergraduate minority student as part of a summer reserarch internship. How have the results been disseminated to communities of interest? Four presentations about the project were given to foresters, entomologists, and pathologist: Kolb, T.E., M.L. Gaylord. 2013. Interactions among drought, tree stress, and bark beetles in forests and woodlands of the southwestern U.S. (abstract). Proceedings of the 2013 Western Forest Insect Work Conference, March 4-7, 2013, Coeur d’ Alene, Idaho. Kolb, T.E., M.L. Gaylord. 2013. Interactions among drought, tree stress, and bark beetles on the Colorado Plateau (abstract). Proceedings of the 12th Biennial Conference of Science and Management on the Colorado Plateau, September 16-19, 2013, Flagstaff, Arizona. Burr, S.J., T.E, Kolb, R.W. Hofstetter, M.K. Gaylord. 2013. Physiological impacts to Pinus ponderosa following colonization of bark beetles and their associated fungi (abstract). Proceedings of the 64th Western Forest Insect Work Conference, March 4-7th, 2013, Coeur d’Alene, Idaho. Reyes, T., S. Burr, R. Hofstetter, T. Kolb. 2013. Attractiveness of frontaline and endo-brevicomin aggregation pheromones to Dendroctonus bark beetles (abstract). Proceedings of the 12th Biennial Conference of Science and Management on the Colorado Plateau, September 16-19, 2013, Flagstaff, Arizona. What do you plan to do during the next reporting period to accomplish the goals? All studies described above will be continued. Training of graduate student will continue.

Impacts
What was accomplished under these goals? A doctoral-level graduate student, Stephen Burr, was recruited for the project in 2012. He worked with the project PI to start a novel experimental study in 2013 on the role of fungi, bark beetles, andtree stressin tree physiological disfunction, and a second project on performance of different bark-beetle-vectored fungi in ponderosa pine trees. These projects are entering their second year and will be continued for at least one more year. An additional pilot project was started on using genomics to identify the microbial community carried by bark beetles. The project team described the main project to natural resource managers and scientists in four different presenations in 2013.

Publications

• Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Burr, S.J., T.E, Kolb, R.W. Hofstetter, M.K. Gaylord. 2013. Physiological impacts to Pinus ponderosa following colonization of bark beetles and their associated fungi (abstract). Proceedings of the 64th Western Forest Insect Work Conference, March 4-7th, 2013, Coeur dAlene, Idaho. Kolb, T.E., M.L. Gaylord. 2013. Interactions among drought, tree stress, and bark beetles in forests and woodlands of the southwestern U.S. (abstract). Proceedings of the 2013 Western Forest Insect Work Conference, March 4-7, 2013, Coeur d Alene, Idaho. Kolb, T.E., M.L. Gaylord. 2013. Interactions among drought, tree stress, and bark beetles on the Colorado Plateau (abstract). Proceedings of the 12th Biennial Conference of Science and Management on the Colorado Plateau, September 16-19, 2013, Flagstaff, Arizona. Reyes, T., S. Burr, R. Hofstetter, T. Kolb. 2013. Attractiveness of frontaline and endo-brevicomin aggregation pheromones to Dendroctonus bark beetles (abstract). Proceedings of the 12th Biennial Conference of Science and Management on the Colorado Plateau, September 16-19, 2013, Flagstaff, Arizona.